“I’m not even sure bisexuality exists. I think it’s just a layover on the way to gaytown.”

– Carrie Bradshaw (Sex and the City)

Many of you are probably familiar with the popular stereotype that bisexual people are actually closeted gays who just aren’t quite ready to admit it to the world. Proponents of this stereotype were seemingly validated by a 2005 study published in Psychological Science, which found that most men who identified as bisexual exhibited stronger genital arousal in response to male pornographic imagery than female pornographic imagery [1]. However, a more recent study published in Biological Psychology disputes this finding and presents convincing scientific evidence that "true" bisexuality (i.e., strong attraction to both men and women) does indeed exist [2].

Both of these studies employed identical methods. In each case, a sample of self-described heterosexual, homosexual, and bisexual men was recruited. All participants were exposed to a series of videos that alternated between non-sexual content, man-on-man pornography, and woman-on-woman pornography. As they watched these videos, the male participants were hooked up to a device that measured changes in penile size (i.e., sexual arousal). The only difference between the studies was in how bisexual participants were recruited. In the original Psychological Science report, bisexual participants were selected based only upon their self-reported sexual orientation (i.e., the only criterion was that they had to identify as bisexual). In the more recent Biological Psychology report, bisexual participants were selected only if they confirmed a history of sexual and romantic relationships with members of both sexes (this was to help ensure that participants’ sexual identities and behaviors were consistent).

The results for heterosexual and homosexual participants were consistent across studies and were exactly what you would expect (i.e., genital arousal was strongest when exposed to pornographic imagery featuring members of their desired sex). The findings for bisexual men were more surprising and each study reported a completely different pattern of results. In the original report, male participants' genital arousal was almost always stronger in response to men (same sex) than women (opposite sex), consistent with the stereotype that bisexuals are just “latent homosexuals.” However, in the more recent study, most bisexual men exhibited very high levels of genital arousal in response to both male and female pornography, providing evidence of true bisexuality. Bisexual men didn't necessarily show equally strong arousal to both sexes, but they at least showed high levels of arousal in each case.

Combined, these studies tell us that bisexuality is a complex identity that means different things to different people and the way researchers define it has implications for the kinds of results they obtain. For some people, bisexuality represents strong attraction toward both men and women. For others, a bisexual identity may signify openness to new experiences, confusion or discomfort with one’s sexuality, or a number of other things. Although much more research is needed on this topic (especially research that includes both male and female participants), these findings provide evidence that bisexuality is a distinct sexual orientation that should not be so quickly dismissed.